chapter 7 chem 100

What is a chemical reaction?

A process that produces new substances.

What are reactants?

Starting substances in a reaction.

What are products?

Substances formed during a reaction.

What does —>mean?

Produces or yields.

What is a physical change?

A change without forming a new substance.

What is a chemical change?

A change that forms new substances.

What does (s) mean?

Solid

What does (l) mean?

Liquid

What does (g) mean?

Gas

What does (aq) mean?

Aqueous — dissolved in water.

What are four possible signs of a chemical reaction?

Color change, temperature change, gas formation, precipitate formation.

Are bubbles always evidence of a reaction?

No. Shaking water produces bubbles physically.

What happens when chalk reacts with acid?

CO2 gas forms.

Must every reaction change temperature?

No. Some reactions have no noticeable temperature change.

Why balance chemical equations?

Law of Conservation of Mass.

What is the Law of Conservation of Mass?

Matter cannot be created or destroyed in a chemical reaction.

What is a coefficient?

A number before a chemical formula.

What is a subscript?

A small number showing the number of atoms.

Can subscripts change when balancing?

No! Change coefficients only.

Balance H2 + O2—>H2O

2H2 + O2—> 2H2O

Balance C3H8+ O2—>CO2 + H20

C3H8 + 5O2 —>3CO2 + 4H2O

Which elements do you balance first in hydrocarbon combustion?

Carbon —> Hydrogen—> Oxygen.

How many oxygen atoms are in 3CO2?

3 * 2 = 6 oxygen atoms.

What does soluble mean?

Dissolves in water.

What does insoluble mean?

Does not dissolve significantly in water.

Are nitrate (NO3-) compounds soluble?

Yes, always soluble in standard solubility rules.

Is CaCO3 soluble?

No, insoluble.

Is BaSO4 soluble?

No, insoluble.

Is LiNO3 soluble?

Yes, soluble.

What are spectator ions?

Ions that remain unchanged during a reaction.

How does KNO3(aq) separate?

K+º(aq) + NO3-(aq)

What is a precipitation reaction?

A reaction that forms an insoluble solid.

What precipitate forms when AgNO3 reacts with NaCl?

AgCl(s), silver chloride.

Balance: H2+ O2—>H20

2H2+ O2—>2H2O

Balance: Al + O2—> Al2O3

4Al + 3O2→ 2Al2O3

What is the precipitate in KI + Pb(NO₃)₂?

PbI₂(s), yellow solid

What are spectator ions?

Ions unchanged on both sides of an ionic equation.

Which ions are spectators in AgNO₃ + NaCl?

Na⁺ and NO₃⁻

What is the net ionic equation for AgCl?

Ag⁺(aq) + Cl⁻(aq) → AgCl(s)

What happens when Zn reacts with CuCl₂?

Zinc replaces copper, forming ZnCl₂ and Cu.

Are nitrate compounds soluble?

Yes, nitrate salts are soluble in water.

What is the difference between a coefficient and a subscript?

Coefficient = number of molecules/formula units; subscript = atoms within a formula unit.

What is the pattern for double displacement?

AB + CD → AD + CB(switch partners)

Synthesis

A + B → AB (combine)

Decomposition

AB → A + B (break apart)